U.S. Pat. No. 4,369,888 describes an opening device which forms the whole closure for a metal container. A neck part of the closure snaps around a locking shoulder on the container. A plug section is hinged to the neck part and is folded into the neck part to close the container. A vent hole in the plug section is closed by a lug on an integral ring pull, which is hinged to the plug at the opposite end to the plug-neck fulcrum.
The hinge between the ring pull and plug sections of the opening device of U.S. Pat. No. 4,369,888 is relatively fragile and may become detached during opening or before removal of the plug can be initiated. Furthermore, the opposing hinges require a high pull force if the plug is to be removed simply by pulling on a ring pull which is attached to the plug at the opposite end to the plug-neck fulcrum. In addition, the device requires special features on the can neck opening to which the closure neck part is directly fixed. The metal of the can body is very thin and the shoulder formed on the can body neck is subject to significant forces when the closure is opened which may deform the shoulder and compromise any seal for recloseability or risk the entire closure being removed from the container.
Continental Can's patent no. FR 1434827 describes a metal can end having a plastics opening device which has a tubular part in an opening of the can end. A tear strip is defined by a score between the tear strip and the tubular part, on the underside of the opening device and inside the container to which the device is attached. The tubular part is said to provide a bore seal with the can end opening and a peripheral edge on the tubular part opposes movement of the tubular part out of the can end opening. However, whilst this patent states that the opening device is easy to open, there is clearly a major risk of accidental opening due to premature tearing of the score or distortion of the plastics opening device when the container is dropped or mishandled in any way. Similarly, if the container is used for carbonated beverages, which are transported or maintained in high ambient temperatures, the soft plastic may deform or creep, leading to product leakage. Most importantly for the context of the present invention, once the opening device of FR 1434827 has been opened and the score broken, the device is not capable of reclosing to prevent spillage and maintain residual carbonation.
This invention seeks to provide an opening device which is capable of reclosing a container, which requires reduced opening force in comparison with the prior art and is easy to manufacture, assemble and operate. Furthermore, the opening device of the invention is adapted to use for packaging carbonated beverages and for use in hot countries. The opening device, whilst being easy to open and reclose, is configured so that creep of the plastic will tend to improve rather than compromise the sealing characteristics.